Conventionally known optical modules include an optical module described in Patent Document 1. In this optical module, as shown in FIG. 18, a substrate 30 is provided with two V-grooves 31 and 32 having different shapes. A cladding 33b of an optical fiber 33 is fixed to one of the V-grooves, namely the V-groove 31. The cladding 33b is positioned by a rising slope 36 defining the boundary between the V-grooves 31 and 32. A mirror (reflection surface) 34 is formed on the front end of the other V-groove 32. This mirror 34 changes the optical axis of a core 33a of the optical fiber 33. A light receiving element 35 mounted on the substrate 30 receives an optical signal from the optical fiber 33.    Patent Document 1: Japanese Patent Application Publication No. H9-54228
However, in the optical module described above, there is a long distance from the front end 33c of the core 33a of the optical fiber 33 to the mirror 34. This cause a light flux emitted from the core 33a to be expanded, resulting in deterioration of optical coupling efficiency.